How (and how often) to test Aquarium Water for Healthy Fish And Plants

How (and How Often) to Test Aquarium Water for Healthy Fish and Plants

Regular water testing is vital for keeping tabs on the health of your aquarium fish and plants, but most beginners in the fishkeeping hobby are not aware of the importance of this practice. People can clean out an aquarium if it is dirty-looking. In reality, aquarium water contains invisible waste chemicals from the fish’s poop and other compounds that can be dangerous at high enough levels. Test kits are the only way to accurately measure if your water is clean and safe enough for fish and plants to live in.


How to test water in a fish tank

Test strips are the most common type of water test for fishkeepers. The chemical reagent is added to a sample of aquarium waters and the color changes according to the water parameter being tested. After a time period, the reagent can be compared to a chart to show the final results. Here are some of the parameters we recommend:

1. Ammonia:Ammonia is created by your fish and other invertebrates through their waste. It is very toxic to animals, especially in water with high pH, and should stay at 0 ppm (parts per million). Measure it with the Ammonia Test Strips.

Aquarium Co-Op Ammonia Test Strips

1. Nitrite When an aquarium is mature and cycled, beneficial bacteria consumes ammonia to make nitrite. Nitrite is also toxic to animals and can burn fish gills and skin, so keep it at 0 ppm. Multi-Test Strips can be used to measure it. 2. Nitrate: In a mature aquarium, another type of beneficial bacteria consumes nitrite and produces nitrate, which is less toxic to fish. As a general rule, we recommend keeping nitrate at 50 ppm or below. Aquarium plants consume nitrate as food so it is important to maintain a minimum of 20 ppm. It can be measured with Multi-Test Strips. Read our article on nitrate to find out more. 3. Chlorine: If your drinking water comes from a municipal water supply, then most likely it is disinfected with chlorine or chloramine to eliminate pathogens. These same chemicals are lethal to animals, so a dechlorinator must be used to make the tap water safe. To make sure your chlorine is at 0 ppm, measure it with Multi-Test Strips.

Aquarium Co-Op Multi-Test Strips

1. pH:PHP tells you how basic or acidic the water is. Most freshwater fish can live at pH levels between 6.5 to 8.0, but some species prefer lower or higher pH. It can be measured with multi-test strips or the API High Range Acid pH Test Kit.

API pH Test with High Range

1. GH: The General Hardness (GH), which measures how hard or hard water is, is measured either in dGH or ppm. Minerals are essential for healthy animal and plant growth, so we recommend keeping between 4-8 dGH (or 70-140 ppm) for most freshwater aquariums. It can be measured with Multi-Test Strips and the API GH & GH Test Kit Combo. 2. H: The water’s buffering capacity is measured by carbonate hardness (KH). KH is a measure of the water’s ability to withstand rapid changes in pH. This can pose a danger to fish. It can be measured in dKH, or degrees of KH, just like GH. We recommend keeping it below 3 dKH (50 ppm), for freshwater aquariums. This will prevent any pH swings. It can be measured with Multi-Test Strips, or the API GH & H Test Kit Combo.

API H & KH Testing Kit Combo

1. Phosphate –Phosphate, a macronutrient, is what plants need to grow well. However, excessive phosphate can lead to algae growth and damage fish health if it is too high. Each aquarium is different and each fish and plant stocking levels are different. However, hobbyists recommend a minimum of 0.5-2 ppm for low-light tanks and 3 ppm for high-light aquariums that use CO2 injection. Measure it with the API Phosphate Test Kit.

API Phosphate Test Kit

1. Copper: Invertebrates are especially sensitive to even trace amounts of copper in the water, but some medications contain copper to treat certain fish diseases. Use the API Copper Test Kit to measure the presence of copper in your tap water or to dose the correct amount of copper-based medication for sick fish.

API Copper Test Kit

1. CO2 This quick test is for measuring the dissolved CO2 content in your aquarium. It can be used either to set up a DIY system or pressurized CO2 systems. The prepared test tube should be filled halfway with water. After shaking for a few seconds you can compare the results to the color chart. This will show you if there is too much, too little or the right amount.

Dennerle CO2 Quick Test


When and How Often to Test Aquarium Water

Ideally, water should be tested as often as possible, but in the past, test kits were often time-consuming and cost prohibitive to use very often. If fish keepers saw something odd in their tanks, they might ignore the problem and avoid testing the water because of these obstacles. Therefore, we developed the Aquarium Co-Op test strips to be faster and cheaper to use so that you can test more frequently for peace of mind. These are some of the most common situations in which you should test your water.

1. New Aquarium When setting up a new fish tank, it takes a while to cycle the aquarium so that the biological filtration is mature enough to purify the water from your fish’s toxic waste. While the aquarium is cycling, it is important to frequently test the water on a daily basis to make sure the ammonia, nitrite, and nitrate levels do not get too high, so get the Ammonia Test Strips and Multi-Test Strips. If you get consistent safe and repeatable results, you can reduce testing to every three days. Then, test once a week. Finally, test once a month. Read our complete article to learn more about the aquarium cycle.

1. Tank Maintenance Once your aquarium is cycled, you may only need to use the Multi-Test Strips every 2-4 weeks to check the nitrate level, which can become toxic at very high levels. Generally speaking, we aim to keep nitrate at 50 ppm or below. If the nitrate reading is higher than 50 ppm or lower, then it’s time to change your water. One of the main reasons we keep live plants within our aquariums is to help reduce the need for water changes. You can use our water chart flow diagram to determine how often water changes should be made based on your nitrate reading.

1. Missing Fish If any of your animals show signs or are acting strangely, you should check all parameters to determine the cause. Begin by checking the water temperature and multi-test strips. Use the API High Range Acid pH Test Kit if you suspect an abnormal rise in pH. Invertebrates like shrimp and snails are more susceptible to copper, so if you notice changes in their health, check your water with the API Copper Test Kit. The key is to not only determine if the measurements are within a healthy range but also to evaluate if they differ greatly from the usual values you have seen in the past.

Abnormal or rapid changes in water parameters can cause health issues in fish.

1. Healthy Plants It is important to monitor nitrate levels when balancing lighting and nutrients in a plant aquarium. Multi-Test Strips are used to measure the nitrate levels. It should be between 25-50ppm. If nitrate is below this amount, then it may be time to dose some Easy Green all-in-one fertilizer to replenish the nutrients in the water. If there is an excess or a shortage of phosphate, it can cause algae growth or leaves with large holes. The API Phosphate Test Kit will help you determine the situation. Finally, if you are adding CO2 gas to the water to increase plant growth, get a read on how much dissolved CO2 is in the aquarium with the Dennerle CO2 Quick Test.

1. Outdoor Pond Large outdoor ponds that have large volumes of water should be tested at least three to five times per year with the Multi-Test Strips or Ammonia Test Strips. The water quality should be checked at the beginning of each season to determine how it has fared in the winter. Check the water quality in the middle of summer. The fish have been eating different foods and the pond evaporates more quickly during warmer weather.

At the end of pond season, make sure all the water parameters are safe before preparing for the cold weather. Finally, it may be good to do an extra test in the middle of winter to see how the fish are doing.

Water test kits can be used for both aquariums and outdoor ponds.

The more mature and problem-free a fish tank is, the less frequently we tend to test it, but don’t forget that your aquarium is a living ecosystem and things are constantly changing. You should test your aquarium again if you travel, change fish food, buy or sell fish, add or remove plants or make other changes to the tank. Hobbyists often keep track of water parameters by writing them down in a journal, or using a spreadsheet. For a fish room with multiple tanks, our CEO Cory will mark the results down on blue painter’s tape and stick it directly on the aquarium glass.

To learn more about water chemistry, we’ve gathered a series of articles to help you increase your knowledge and enjoyment of the fishkeeping hobby. Take a look at them and get out there enjoying nature everyday!